JPS6344759B2 - - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to an improved process for preparing alkoxyalkyl triorganophosphates using a continuous alkoxidation process.

Triorganic phosphates are generally produced on a relatively small scale compared to inorganic phosphates. A suitable batch process for the production of trialkoxyalkyl phosphates is described in U.S. Pat.
Disclosed in No. 3020303. Such a process involves reacting a mixture containing 3 to 4 moles of alkali metal hydroxide and about 6 moles of aliphatic alcohol (having 1 to 18 carbon atoms) per mole of phosphorous oxychloride, while simultaneously to produce a substantially anhydrous reaction mixture containing an alkali metal alcoholate, and the alcoholate and phosphorous oxychloride are removed under a non-oxidizing atmosphere to produce a substantially anhydrous reaction mixture containing an alkali metal alcoholate,
The method includes the steps of reacting at a temperature of from 100°C to produce a product mixture containing the phosphate ester alcohol, and separating the ester from the product mixture. This batch process yielded a product with a good color appearance of about 50 on the platinum-cobalt scale (ASTM D1209).

This batch process is suitable for producing several products in the same equipment. When a batch process is changed to a continuous process, trialkoxyalkyl phosphates such as tributoxyethyl phosphate with poor color reproduction are produced, but tributyl phosphate with good color reproduction is produced using the same continuous process equipment. Can be manufactured. Although poorly colored trialkyloxyphosphates can be treated to remove color, it is desirable to avoid such treatments.

The present invention provides an alkoxyalkyl triorganophosphoric acid using a continuous process for producing alkoxyalkyl alkoxides, which includes a step of treating an alkoxyalkanol with sodium borohydride (NaBH ₄ ) for 20 minutes to 4 hours before using the alkoxyalkanol in a continuous alkoxidation reaction. Provides a method for producing esters.
After treatment with sodium borohydride, the alkoxyalkanol (hereinafter referred to as alcohol) is reacted with an alkali metal hydroxide, preferably sodium hydroxide, and dehydrated in a continuous reaction to synthesize the alkali metal alkoxide. Using too much alcohol. The alkoxide is phosphorylated by reaction with phosphorous oxychloride to form the crude trialkoxyalkyl phosphate. Both the alkoxidation and phosphorylation reactions are carried out in a non-oxidizing atmosphere. The crude product is then purified by drowning, i.e. washing with water to remove salt reaction products, stripping to remove excess alcohol,
Washing removes other undesirable impurities and residual salts, followed by drying to remove residual moisture. The color of the final product is 25 to 200 (platinum cobalt color).

Alcohols useful in this method include alkoxyalkyl-substituted carbinols, i.e., those having the structural formula R ₁ -
Included are alkoxyalkanols of OR ₂ --OH (wherein R ₁ contains 1 to 6 carbon atoms and R ₂ contains 1 to 4 carbon atoms). Included are alkoxyalkanols such as 2-methoxyethanol, 2-ethoxyethanol, 2-butoxyethanol, 2-iso-propoxyethanol and 2-hexoxyethanol. These mixed carbinols have chain lengths of 2 to 18 carbon atoms.

Alkali metal hydroxides used in the process include sodium, potassium or lithium hydroxide, with sodium hydroxide being preferred for economic reasons.

A typical example of the method is described using 2-butoxyethanol and sodium hydroxide. 2-
Treat the butoxyethanol with sodium borohydride for 20 minutes to over 4 hours. The treated 2-butoxyethanol is then continuously vaporized and continuously fed to the lower part of the dehydration tower reactor. Sodium hydroxide is continuously fed in solution to the top of the column reactor and reacts with vaporized 2-butoxyethanol placed near the bottom of the column.

A 2-butoxyethanol-water azeotrope is formed at the top of the column and is removed from the top of the column and concentrated. The upper concentrate is separated into an organic phase containing 2-butoxyethanol and an aqueous phase. The aqueous phase (water) is removed from the process and the 2-butoxyethanol is returned to the top of the column. The product leaving the column reactor was analyzed and contained approximately 20-30% alkoxide. If desired, a portion of the excess alcohol may be removed and concentrated prior to phosphorylation. Typically, sodium hydroxide is fed to the column as a concentrated solution, such as a 50% solution. The sodium hydroxide and gaseous alkoxyalkyl-substituted carbinol feed rates are adjusted to the capacity of the equipment to ensure that substantially all of the hydroxide is reacted and to remove water from the system. When using 50% aqueous sodium hydroxide and vaporized 2-butoxyethanol, best results are obtained if the temperature in the center of the column is maintained at about 120°C. Obviously, the control point can be located other than centrally within the column and different control temperatures can be used.

The alkoxide, 2-butoxyethoxide, is then fed to a continuous or batch phosphorylation reaction. The process, whether continuous or batchwise, is carried out as disclosed in US Pat. No. 3,020,303. That is, the alkoxide reaction mixture is cooled to below 50°C, preferably from 25 to 50°C. The cooled alkoxide is reacted with phosphorous oxychloride while maintaining the temperature below 100°C, preferably between 30 and 60°C. Faster reaction rates can be used by cooling the reaction mixture.
A phosphate ester, such as tributoxyethyl phosphate, is treated with sufficient water to dissolve the alkali metal salt. Up to this point the alkoxidation and phosphorylation reactions are carried out in a non-oxidizing atmosphere, but after removing the salt a non-oxidizing atmosphere is no longer needed.
The crude ester is then separated from the salt solution. The crude ester may be purified in any desired manner. For example, unreacted alcohol can be recovered from the crude ester by distillation. The alcohol can then be recycled to the process.

The following examples further illustrate the method of the invention.
All parts and percentages are by weight unless otherwise noted.

Comparative Example A 5.22 as a 50% solution under a pressure of 14.33 KPa (15.6° C.) while feeding vaporized 2-butoxyethanol near the bottom of the column at a rate to react with substantially all of the hydroxide fed. Kg/min (100%
The continuous alkoxidation reaction is carried out in a dehydration tower reactor in which sodium hydroxide fed at a rate of (with respect to NaOH) can be reacted. Use 300% excess alcohol. Excess alcohol forms an azeotrope with the water in the hydroxide solution and the water formed during the alkoxidation reaction. The azeotrope is removed from the top, concentrated and separated into alcoholic and aqueous phases. Water is removed from the process and alcohol is returned to the process near the top of the dehydration tower reactor. When the temperature at the center of the tower is maintained at 120℃,
The reaction product removed from the bottom of the column reactor is 25%
is sodium butoxyethoxide and 0.065
% sodium hydroxide. sodium 2
The -butoxy ethoxide reaction product was cooled to 50°C and then slowly reacted with phosphorus oxychloride while cooling in a nitrogen atmosphere while maintaining the temperature of the phosphorylation reaction mixture at 50°C. When the phosphorylation reaction was completed, enough water was added to the phosphorylation reaction mixture with vigorous stirring to obtain a 20% NaCl solution.
The salt solution was separated from the crude phosphate ester reaction mixture. The phosphate ester was distilled to remove excess alcohol and recycled to the process. The phosphate ester was washed with 1% sodium hydroxide solution and then twice with water. Next, the phosphate ester was dried and the color was measured, which showed that it was on the Pt-Co scale (ASTMD1209~
79) and it was 150.

EXAMPLE OF THE INVENTION The procedure of the comparative example was repeated except that the 2-butoxyethanol was treated with 250 ppm sodium borohydride. Before using the 2-butoxyethanol, add the sodium borohydride to the 2-butoxyethanol with stirring as a stabilizing solution containing 12% sodium borohydride, 40% sodium hydroxide, and 48% water. , left for 20 minutes. 3.7 Kg/min (8.1 lb/min) of 50% aqueous solution of sodium hydroxide
(with respect to 100% NaOH) to the dehydration tower reactor. 2- treated with sodium borohydride
Butoxyethanol is vaporized at 175℃, 37.33KPa
(15.6°C) was fed to the column. The reaction product mixture is 25% butoxyethoxide;
Contained 0.062% sodium hydroxide. When the phosphorylation reaction was carried out, the color of purified trisbutoxyethyl phosphate was 40 (Pt-Co color). 100ppm for processing 2-butoxyethanol
When the example of the present invention was repeated using sodium borohydride, the color representation of trisbutoxyethyl phosphate was 100.

Claims (1)

[Claims] 1 Structural formula R ₁ -O-R ₂ OH (wherein R ₁ contains 1 to 6 carbon atoms, and R ₂ contains 1 to 4 carbon atoms) )
6 moles of alkoxyalkanol of (a) are continuously reacted with 3 to 4 moles of alkali metal hydroxide in a non-oxidizing atmosphere to produce the corresponding alkali metal alkoxide, and at the same time the substance of the water produced during the reaction is (b) reacting the reaction mixture with phosphorous oxychloride in a non-oxidizing atmosphere at a temperature of 0 to 100° C. to form the product ester of said alcohol; (c) separating the ester from the reaction mixture; A method characterized by treating an alkoxyalkanol for 20 minutes. 2. In the method described in claim 1,
Alkoxyalkanols include 2-methoxyethanol, 2-ethoxyethanol, 2-butoxyethanol, 2-iso-propoxyethanol and
- A method characterized in that it is selected from hexoxyethanol. 3. In the method described in claim 2,
A method characterized in that the alkoxyalkanol is 2-butoxyethanol. 4. In the method according to claim 2 or 3, sodium borohydride is added to alkoxyethanol as a solution containing 12% sodium borohydride, 40% sodium hydroxide, and 48% water. A method characterized by: